docs: def parse(item):
          r"""
          >>> Tag.parse('x') == {'key': 'x', 'value': None}
          True
  
          >>> Tag.parse('x=yes') == {'key': 'x', 'value': 'yes'}
          True
  
          >>> Tag.parse('x=3')['value']
          '3'
  
          >>> Tag.parse('x=red fox\\:green eggs')['value']
          'red fox;green eggs'
  
          >>> Tag.parse('x=red fox:green eggs')['value']
          'red fox:green eggs'
  
          >>> Tag.parse('x=a\\nb\\nc')['value']
          'a\nb\nc'
          """
          key, sep, value = item.partition('=')
          value = value.replace('\\:', ';')
          value = value.replace('\\s', ' ')
          value = value.replace('\\n', '\n')
          value = value.replace('\\r', '\r')
          value = value.replace('\\\\', '\\')
          value = value or None
          return {
              'key': key,
              'value': value,
          }